This is an old revision of the document!
How to scan computers/network with Nmap
First of all, we are going to discover some computers in our network (192.168.0.0)
santi@kalibook:$ nmap -sn 192.168.1.0/24 Starting Nmap 6.49BETA4 ( https://nmap.org ) at 2017-09-10 20:05 CEST Nmap scan report for 192.168.1.1 Host is up (0.017s latency). Nmap scan report for 192.168.1.3 Host is up (0.013s latency). Nmap scan report for 192.168.1.29 Host is up (0.00040s latency). Nmap scan report for 192.168.1.32 Host is up (0.074s latency). Nmap scan report for 192.168.1.254 Host is up (0.010s latency). Nmap done: 256 IP addresses (5 hosts up) scanned in 9.61 seconds
Imagine that you want to guess which operating system is running in some of the computers you have scanned. In this case we will do with a computer that is running a Windows 7 OS). We know the IP address of this computer because it is a Virtual Machine that it is running in this moment. It does not appears in the list of remote computers because its Firewall is enabled. If we disabled the Firewall and we try again to scan our network, this computer will appear in the list of connected computers.
Now, we are going to scan this computer to try to guess which kind of OS is running and some extra information. First, we will try with the Firewall enabled:
santi@kalibook:$ sudo nmap -O 192.168.1.40 Starting Nmap 6.49BETA4 ( https://nmap.org ) at 2017-09-10 20:05 CEST Nmap scan report for 192.168.1.40 Host is up (0.00018s latency). All 1000 scanned ports on 192.168.1.40 are filtered MAC Address: 08:00:27:5C:0E:94 (Cadmus Computer Systems) Too many fingerprints match this host to give specific OS details Network Distance: 1 hop OS detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 30.73 seconds
We can see that we did not obtain any information abut the remote computer. Then, we will disabled the default Firewall and we will try again with the same nmap options:
santi@kalibook:$ nmap -O 192.168.1.40 Starting Nmap 6.49BETA4 ( https://nmap.org ) at 2017-09-10 20:07 CEST Nmap scan report for 192.168.1.40 Host is up (0.00016s latency). Not shown: 990 closed ports PORT STATE SERVICE 135/tcp open msrpc 139/tcp open netbios-ssn 445/tcp open microsoft-ds 5357/tcp open wsdapi 49152/tcp open unknown 49153/tcp open unknown 49154/tcp open unknown 49155/tcp open unknown 49156/tcp open unknown 49158/tcp open unknown MAC Address: 08:00:27:5C:0E:94 (Cadmus Computer Systems) Device type: general purpose Running: Microsoft Windows 2008|10|7|8.1 OS CPE: cpe:/o:microsoft:windows_server_2008::sp2 cpe:/o:microsoft:windows cpe:/o:microsoft:windows_7::- cpe:/o:microsoft:windows_7::sp1 cpe:/o:microsoft:windows_8 OS details: Microsoft Windows Server 2008 SP2 or Windows 10 Tech Preview, Microsoft Windows 7 SP0 - SP1, Windows Server 2008 SP1, Windows 8, or Windows 8.1 Update 1 Network Distance: 1 hop OS detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 103.30 seconds
Because the firewall was disabled we have obtained a lot of information about the remote computer: open ports, services running, MAC address and some extra information about which version of Windows is running and a aproximation about how updated it is (Service Packs installed on remote computer). Now we can see how importat is to enable our Firewall in our computer. If some attacker does not know nothing about our computer it will be more difficult to receive any kind of attack from anyone.
santi@kalibook:$
santi@kalibook:$
santi@kalibook:$